Lifespan and Causes of Death in the Irish Wolfhound - Vetsuisse ...

falsely) drop. The extent of this bias depends on the structure of the available
longevity data – in Wolfhounds, dogs born less than 12 years before the end of the
data collection period can be expected to be subject to it. Naturally, the bias grows
stronger as the whelping date approaches the end of the data collection period.
In explaining this to a lay public, I have found the following example to be very useful:
If we imagine a litter of 10 individuals born 6 years ago, out of which 3 dogs died at
age 5, this does not imply that the average lifespan for the litter was five years.
Average lifespan can only be determined after all 10 dogs are dead. This is obvious
when we consider the year of birth, but becomes masked when considering the year
of death.
3.1.2 Scientific Publications
3.1.2.1 Comfort
While it is generally agreed upon that Wolfhounds as a breed have a below-average
life expectancy, relatively little scientific work has been done on the topic. The first
paper on the subject was published 50 years ago based on individuals born in one
kennel between 1927 and 1945 (Comfort 1956). It found a median age at death of
4.95 ± 0.94 years for males and 6.59 ± 0.95 years for females who had survived their
first year of life. The maximum ages in his sample of 154 animals were 10.5 years in
males and 13.42 years in females.
Comfort found a high mortality during the first year of life, with a chance of reaching
one year of age of only 61.29% for males and 72.92% for females born alive.
Interestingly, the overall survival curve was linear rather than sigmoid, indicating a
relatively high mortality at a young age. Given that effective vaccines and antibiotics
were not available at the time, this high death rate was probably caused by infectious
diseases.
Although Comfort does not give the relative importance of different causes of death
for the overall population, he mentions that of the twelve males who died in their third
year of life, four died from distemper, four from gastroenteritis, two of infectious
pneumonia, one of unknown causes and one was "destroyed as a result of persistent
fits".
In the older animals, Comfort found that three of the four oldest males died of "heart
disease", while the three oldest bitches all died of mammary carcinoma. One nineyear-old
bitch died of uterine carcinoma, and no tumours were recorded in any of the
males. This is a remarkable observation when considering the high incidence of
Osteogenic sarcoma in the breed nowadays (see chapter 3.4).
While he did not investigate the relation between lifespan and inbreeding, Comfort
argued that Wolfhounds had probably reached a point where a stable lifespan was
established that would not be subject to further inbreeding depression, comparable to
the situation that occurs in inbred strains of Drosophila melanogaster.
In a follow-up study, Comfort provided survival information of an additional ten
Wolfhounds from the same kennel, which were not significantly different from his
10